The proposed study is the continuation of a long-term investigation of the neuronal, neurochemical, hodological, and synaptic organization of the lateral and basolateral nuclei (L-BL) of the mammalian amygdala. Previous studies in this laboratory have provided important new information regarding the projections and transmitter immunohistochemistry of L-BL in the rat. The proposed investigation will explore additional hodological and neurochemical aspects of L-BL in the rat and will initiate similar studies of homologous nuclei in the primate amygdala. Studies in the rat will: 1) determine which cell types utilize glutamate as a neurotransmitter; 2) determine if the neuropeptides vasoactive intestinal polypeptide (VIP), and somatostatin (SOM) and cholecystokinin (CCK) are found in neurons that also contain the inhibitory neurotransmitter gamma-aminobutyric acid (GABA); 3) examine the precise pattern of termination of afferents to L-BL from various brain regions; 4) analyze the synaptology of neurons identified by immunocytochemical techniques. Studies in primates will: 1) describe and classify the different types of L-BL neurons on the basis of morphological differences in Golgi-stained brains; 2) characterize the cell types that contain VIP, SOM, CCK, GABA and glutamate; 3) determine if the neuropeptides coexist with GABA in some neurons. The techniques used to accomplish these aims include the Golgi technique, immunocytochemistry at the light and electron microscopic levels, and PHA-L anterograde tract tracing technique. Computer-assisted statistical procedures will be used to correlate neurons stained by different techniques. The amygdala is one of two major forebrain areas involved in learning and shows neuropathological alterations in Alzheimer's disease. It is also involved in temporal lobe epilepsy, the most common form of epilepsy and a type frequently associated with aggression and other psychopathological changes. Amygdaloid levels of the peptides to be investigated in the proposed study are altered in schizophrenia and in the development of epileptic phenomena in this area. It is also known that the chief site of the anti-anxiety and anti-convulsant actions of the GABA-related benzodiazepine drugs (Valium and Librium) is L-BL. Information on the connections and chemical microcircuitry of L-BL should contribute to an understanding of its pharmacology, physiology and pathophysiology. Future studies of both rodents and primates in this laboratory will continue to explore important aspects of the neurochemical synaptology of L-BL at the ultrastructural level.